This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Currently, there is no animal model for HIV-1 infection and disease because the virus is highly specific for humans. Macaques are generally resistant to HIV-1, with the exception being pig-tailed macaques. Our lab showed that pig-tailed macaques are unable to express functional isoforms of TRIM5-alpha, which has been identified as a host factor that restricts the replication of HIV-1 in rhesus monkeys. Therefore, it is possible that HIV-1 will only need to overcome restriction by another host factor, APOBEC3G/F, to replicate successfully in pig-tailed macaques. To test this hypothesis, we collaborated with Dr. J. Kimata of Baylor College of Medicine, who engineered an HIV-1 clone that includes the vif gene of SIVmne, allowing it to counteract APOBEC3G/F-mediated restriction. This chimeric virus, HSIV-vif, is 96% HIV-1 and 4% SIV. It replicates in stimulated pig-tailed macaque blood cells as efficiently as SIVmne. In another pilot study, we inoculated 2 juvenile pig-tailed macaques intravenously with HSIV-vif. Although both animals became infected, plasma viremia did not sustain beyond 10 months after infection. Since newborn animals are more susceptible to lentiviral infection and disease, we inoculated two newborn pig-tail macaques with HSIV-vif. Both animals were infected, with a peak plasma viral load of 0.5-1x105 copies/ml. Although viral load decreased to baseline (100 copies/ml) after acute phase infection, it rebounded in both animals between week 28 and 44, indicating persistent infection. Comparative studies allowed us to identified two notable differences between the Pt-tropic HIV-1 and SIVmne (1) SIV Vif does not associate with Pt-tropic HIV-1 viral particles;(2) while Pt-tropic HIV-1 degrades both Pt APOBEC3G and APOBEC3F, it prevents their inclusion in virions to a lesser extent than pathogenic SIVmne. Thus, while SIV Vif is necessary for persistent infection by Pt-tropic HIV-1, improved expression and inhibition of APOBEC3 proteins may be required for robust viral replication in vivo.